DIGITAL EDITION

Accessories for Automating Multicolor Pad Printing

(July 2008) posted on Wed Jul 16, 2008

Automation can improve the quality, consistency, and productivity with high-volume, multicolor pad-printing jobs. This article explores parts-handling devices and other accessories that can improve accuracy and efficiency in your shop.

The rotating fixture is a technical variation on the shuttle that can extend the shuttle’s capabilities (Figure 2). This rotation is accomplished by an actuator that responds to a programmed command. By turning the part in increments of 90°, it allows the printheads to apply an additional image or set of images. This is especially useful for producing custom golf-ball decorations that demand tight, multicolor registration. For most applications, an acceptable tolerance for multicolor images is ±0.002 in. Anything more than that allows fine lines and halftone dots to blur. The result is just not a visually acceptable product.

A word to the wise: Don’t cut corners on that holding fixture or nest. It may be the weakest link in your chain of quality. The worst place to save money is buying second-rate tooling, or even worse—taking the do-it-yourself approach to precision tooling. Fixtures that are too loose or too tight directly impact your quality by producing inconsistent prints and increasing waste. Investing in the best materials and workmanship available will save you money in the long run. Experienced toolmakers are familiar with the clearance and spacing (also called pitch) of specific pad-printing machines. By knowing in advance which machine will be used in the printing system, the tooling designer can make allowances for proper loading and seating of the part in the fixture.

Other reliable auxiliary devices that engineers often specify for multicolor pad-printing applications are the racetrack conveyor, the over-under conveyor, and robotic part-handling devices. All are suited for long runs that require tight registration and durability.

Racetrack The racetrack carries 10-12 platens, each with its own part-holding fixture, in an oval-shaped path. The operator manually loads each fixture opposite the printing station. As each platen moves along the racetrack oval, it makes a 180° turn to face the printing machine, receives the image or images, then proceeds around to return to the unloading station. Racetracks usually employ barrel cam drives to accomplish their positive-stop positioning, which is critical for multicolor jobs. The racetrack is especially desirable for its durability and tight registration throughout long production runs.